4 Week olds with 1 Week olds

I have just gotten the rest of my shipment the other day, and they all came happy and healthy! However, I had already had two baby black silkies that are now about 4 weeks old. The new shipment is almost 1 week old. I had both the black silkies separated from the rest of the flock when I wasn't watching them, and when I was they all hung out together. But whenever they were all together one of the black silkies (Gizmo) would pick on the yellow faverolle (Pumpkin) and the white/yellow cochin (Nugget). Gizmo also picks on one of the ducks I have, Daisy, but Daisy can out run Gizmo and is almost the same size as her.

Should I be worried about Pumpkin and Nugget being picked on too much, or should I just let it happen and stop keeping them separated since they may be just establishing the pecking order?

I don't want Gizmo to cause any serious damage to my other babies while I'm sleeping, thanks to anyone who has any input.

If it's just "friendly" pecking and messing about, I wouldn't worry about it. Just keep an eye on them and see how things go, make sure everyone has access to the feed and water, especially the younger ones, and make sure they have enough space in the brooder to stay out of each others' feathers. I would recommend a minimum of 1 sq foot per chick for these guys, more if you can.